The HFD-WBY commuter rail study is actively ongoing, using the Berlin Branch instead:
http://www.centralctrailstudy.com/" onclick="window.open(this.href);return false;. It's a less convenient route for sure, but in the end little more than a flesh wound for that service's prospects. The additional time penalty isn't huge on a line lots of tangent track (save for the downtown Bristol hairpin) and wide stop spacing. It still handily beats I-84, and as long as that is true the demand's going to be big.
It was actually an ironclad requirement of the Busway funding legislation to fund a couple million for the CR study and get it going right away. That was the compromise Gov. Malloy had to offer to prevent a Senate filibuster mounted by the Bristol/Plainville legislators. You can see on the website they're going at a pretty brisk pace with the meetings. It'll be interesting to see in 1-1/2 to 2 years when they release the final scoping report what ridership figures this turns up, because everybody assumes Malloy funded it to bury it. But that Waterbury/Plymouth/Bristol/Plainville contingent in the Legislature are frothing determined to get this built (at this point it's hard to determine where genuine enthusiasm blurs into Busway spite and making Malloy eat it) and are booby-trapping themselves to force the issue. They may not be in the driver's seat at shaping CDOT's borked-up priorities, but they sure as hell can make a spectacle for themselves if the study ridership comes back slam-dunk for this and re-arm with a lifetime's worth of ammo for Busway critique.
They can definitely build this without need for a 3rd track yet. There's plenty of capacity there to handle the max-rollout NHHS with this service, given that the Springfield Line has such negligible utilization today. All of it has been studied. It's when you get past there...when NHHS is running the fullest schedule modeled in every CDOT study...and further increases are needed that future needs get murky. Because that has not been modeled. Neither have the moderate effects of: Amtrak Inland Regionals, Amtrak Montrealer restoration giving bump to Vermonter frequencies, mixed NHHS service patterns poking north of Springfield on the Knowledge Corridor. Each of those is no-build in CT or (in the case of north-of-SPR commuter service) no-build at all and can appear relatively quickly on the corridor if Massachusetts, Vermont, and/or Quebec go for it with their state-sponsored funding. So add those into the unmodeled traffic mix. It really is not known beyond 10 years what kind of traffic we're going to be dealing with. All bets are off on the future track capacity needs if NHHS significantly overperforms and the auxiliary services start incrementally taking their small slices of the pie.
Unfortunately I haven't read that CDOT traffic engineer's thread on Somethingawful.com ever since the site started requiring a registration to view, so I don't know what he's said about it lately (see the other thread for the money quotes of his blunter observations). Definitely as of late last year CDOT still had
NO final lease agreement with Amtrak for the Busway's use of the ROW. Which means, not only is CDOT actively constructing the Busway while not knowing what the status of its occupancy is should Amtrak need a 3rd track...but Amtrak can gouge them on annual rent. Which is a truly scary proposition as the capital cost spirals up and this detail is yet unresolved. Amtrak is sitting pretty in all this. They're getting a free grade separation in West Hartford, can jack the state up for an overinflated rent, and possibly evict them when they need more tracks while more or less stealing the bridge and culvert infrastructure the state built on their ROW. It cannot be understated how insane and corrupt this project is on every level. They dove head-first into this without basic-most protection of their right of way. This is so ripe for abuse of course Amtrak is going to go along. It's all profit with no downside for them if they can evict when the 3rd track is needed.